Union officials in the fifth-largest U.S. school district don’t know how a free-market think tank obtained teachers’ email addresses to send union opt-out information, but they’re investigating and filing a lawsuit over it.

Nevada’s Clark County School District (CSD) teachers can only leave their local union, the Clark County Education Association (CEA), from July 1 to July 15 each year. The Nevada Public Research Institute recently sent emails to nearly 12,000 teachers informing them of this option.

The district says it did not provide NPRI a list of all 40,000 district teacher email addresses, as it requested in public records request earlier this year. The district says it would not provide the list to any group. In response, CEA officials said the union plans to file a lawsuit against the district for unfair labor practices and will “investigate” the matter internally.

“Make no mistake, NPRI’s campaign to ‘educate’ teachers about the opt-out period had nothing to do with educating teachers,” says Letty Elias, CEA’s associate executive director. “Their campaign had only one goal: to weaken the teachers’ union so they can take away teachers’ voices.”

Two-Week Window Nevada is a right-to-work state, meaning government teachers are not forced to join a union when hired. But many local contracts, including Clark County’s, require teachers to automatically enroll and only allow opting out during two weeks of summer vacation.

The email comes on the heels of a yearlong contract negotiation battle between the district and union over pay increases and layoffs. The district is the largest employer in the state, with more than 37,000 employees.

The Las Vegas Review-Journal found in February that while union bosses complained school administrators are making too much money, they made salaries of $139,000 to $600,000 each, more than triple a new teacher’s average salary. The average teacher’s salary in the district, including benefits, is approximately $74,000. Union dues average $768 a year.

“Nevada currently ranks dead-last in per-pupil spending,” so CEA plans to rev up “political activism” for more funding, Elias said. The district spends approximately $10,000 per student, according to the National Center for Education Statistics, significantly more than the state it ranks last on education spending: Utah spends approximately $6,500 per student.

Union DiscontentThe debate adds to growing discontent with unions nationwide. A recent Harvard University public opinion survey found the number of people who believe unions make a positive contribution to education has decreased from 29 percent to 22 percent in the past year.

NPRI’s effort has had “no significant impact,” on memberships, Elias said. Even so, NPRI plans to continue its work in other counties.

“We want to empower teachers,” Matthews said. “We plan to keep working to get the word out so teachers are at least aware what they can do.”